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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2008 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
.file "strcmp.s"
/* strcmp(s1, s2)
*
* Compare strings: s1>s2: >0 s1==s2: 0 s1<s2: <0
*
* Fast assembler language version of the following C-program for strcmp
* which represents the `standard' for the C-library.
*
* int
* strcmp(s1, s2)
* register const char *s1;
* register const char *s2;
* {
*
* if(s1 == s2)
* return(0);
* while(*s1 == *s2++)
* if(*s1++ == '\0')
* return(0);
* return(*s1 - s2[-1]);
* }
*/
#include <sys/asm_linkage.h>
! This strcmp implementation first determines whether s1 is aligned.
! If it is not, it attempts to align it and then checks the
! alignment of the destination string. If it is possible to
! align s2, this also happens and then the compare begins. Otherwise,
! a different compare for non-aligned strings is used.
ENTRY(strcmp)
.align 32
subcc %o0, %o1, %o2 ! s1 == s2 ?
bz,pn %xcc, .stringsequal ! yup, same string, done
sethi %hi(0x01010101), %o5 ! magic2<31:13>
andcc %o0, 7, %o3 ! s1 sword-aligned ?
or %o5, %lo(0x01010101),%o5! magic2<31:0>
bz,pn %xcc, .s1aligned ! yup
sllx %o5, 32, %o4 ! magic2<63:32>
sub %o3, 8, %o3 ! number of bytes till s1 aligned
.aligns1:
ldub [%o1 + %o2], %o0 ! s1[]
ldub [%o1], %g1 ! s2[]
subcc %o0, %g1, %o0 ! s1[] != s2[] ?
bne,pn %xcc, .done ! yup, done
addcc %o0, %g1, %g0 ! s1[] == 0 ?
bz,pn %xcc, .done ! yup, done
inccc %o3 ! s1 aligned yet?
bnz,pt %xcc, .aligns1 ! nope, compare another pair of bytes
inc %o1 ! s1++, s2++
.s1aligned:
andcc %o1, 7, %o3 ! s2 dword aligned ?
or %o5, %o4, %o5 ! magic2<63:0>
bz,pn %xcc, .s2aligned ! yup
sllx %o5, 7, %o4 ! magic1
sllx %o3, 3, %g5 ! leftshift = 8*ofs
orn %g0, %g0, %g1 ! all ones
and %o1, -8, %o1 ! round s1 down to next aligned dword
srlx %g1, %g5, %g1 ! mask for fixing up bytes
ldx [%o1], %o0 ! new lower dword in s2
orn %o0, %g1, %o0 ! force start bytes to non-zero
sub %g0, %g5, %g4 ! rightshift = -(8*ofs) mod 64
sllx %o0, %g5, %g1 ! partial unaligned word from s2
add %o2, %o3, %o2 ! adjust pointers
nop ! align loop to 16-byte boundary
nop ! align loop to 16-byte boundary
.cmp:
andn %o4, %o0, %o3 ! ~word & 0x80808080
sub %o0, %o5, %o0 ! word - 0x01010101
andcc %o0, %o3, %g0 ! (word - 0x01010101) & ~word & 0x80808080
bz,a,pt %xcc, .doload ! no null byte in previous word from s2
ldx [%o1+8], %o0 ! next aligned word in s2
.doload:
srlx %o0, %g4, %o3 ! bytes from aligned word from s2
or %g1, %o3, %g1 ! merge to get unaligned word from s2
ldx [%o1 + %o2], %o3 ! word from s1
cmp %o3, %g1 ! *s1 != *s2 ?
bne,pn %xcc, .wordsdiffer ! yup, find the byte that is different
add %o1, 8, %o1 ! s1+=8, s2+=8
andn %o4, %o3, %g1 ! ~word & 0x80808080
sub %o3, %o5, %o3 ! word - 0x01010101
andcc %o3, %g1, %g0 ! (word - 0x01010101) & ~word & 0x80808080
bz,pt %xcc, .cmp ! no null-byte in s1 yet
sllx %o0, %g5, %g1 ! partial unaligned word from s2
! words are equal but the end of s1 has been reached
! this means the strings must be equal
.strequal:
retl ! return from leaf function
mov %g0, %o0 ! return 0, i.e. strings are equal
nop
.s2aligned:
ldx [%o1 + %o2], %o3 ! load word from s1
.cmpaligned:
ldx [%o1], %g1 ! load word from s2
cmp %o3, %g1 ! *scr1 == *src2 ?
bne,pn %xcc, .wordsdiffer ! nope, find mismatching character
add %o1, 8, %o1 ! src1 += 8, src2 += 8
andn %o4, %o3, %o0 ! ~word & 0x80808080
sub %o3, %o5, %o3 ! word - 0x01010101
andcc %o3, %o0, %g0 ! (word - 0x01010101) & ~word & 0x80808080
bz,a,pt %xcc, .cmpaligned ! no null-byte in s1 yet
ldx [%o1 + %o2], %o3 ! load word from s1
! words are equal but the end of s1 has been reached
! this means the strings must be equal
.stringsequal:
retl ! return from leaf function
mov %g0, %o0 ! return 0, i.e. strings are equal
nop ! align loop on 16-byte boundary
nop ! align loop on 16-byte boundary
nop ! align loop on 16-byte boundary
.wordsdiffer:
mov 56, %o4 ! initial shift count
srlx %g1, %o4, %o2 ! first byte of mismatching word in s2
.cmpbytes:
srlx %o3, %o4, %o1 ! first byte of mismatching word in s1
subcc %o1, %o2, %o0 ! *s1-*s2
bnz,pn %xcc, .done ! bytes differ, return difference
nop
andcc %o1, 0xff, %o0 ! *s1 == 0 ?
bz,pn %xcc, .done ! yup, strings match
subcc %o4, 8, %o4 ! shift_count -= 8
bpos,pt %xcc, .cmpbytes ! until all bytes processed
srlx %g1, %o4, %o2 ! first byte of mismatching word in s2
.done:
retl ! return from leaf routine
nop ! padding
SET_SIZE(strcmp)
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